It is often desirable to apply clear, pigmented or dyed ink coatings or layers to form distinctive logos or indicia on game balls (e.g., golf balls, ping pong balls, billiard balls, baseballs, basketballs, racquet balls, handballs, etc.). Various commercially available inks are commonly used for this purpose. More than five hundred million golf balls are produced each year, a significant percentage of which have indicia or logos printed on their outer surface. The indicia typically include any one of the golf ball company, tradename, a number, or an image, such as a corporate or country club logo. The most common method for adding a logo to the dimpled surface of a golf ball is by pad printing, although other methods, such as inkjet printing, are adaptable for such surfaces.
Golf balls are commonly one-piece, two-piece or three-piece constructions. One-piece balls are made from a homogeneous polymer shaped into a golf ball. Two-piece golf balls comprise a core and an outer surrounding polymeric cover. Three-piece (or more) golf balls comprise various combinations of a core (wound or unwound), one or more intermediate polymeric shells and an outer polymeric cover. The cover polymer used in two-piece and three-piece balls may, for example, be balata, an ionomeric polymer (e.g., SURLYN®) or a polyurethane.
Golf ball covers are commonly painted with a primer coat, which may be colored (e.g., white) or transparent. Alternately, the cover itself may contain a colorant. Typically, a tough, often glossy, topcoat is applied over the cover and/or the primer coat to form a protective outer seal on the golf ball. The topcoat may comprise, for example, a two-component urethane. The topcoat typically increases the shine (i.e., glossy appearance) and durability of the golf ball to enhance or brighten its appearance.
Most commonly, indicia, logos and production prints are applied to golf balls by a pad printing process and apparatus. Pad printing uses an etched image plate (i.e., a cliché) having a negative etching of the desired image. During pad printing, ink is applied to the image plate, thus filling the etched image. Excess ink is then scraped off of the image plate, leaving behind ink only within the etched image. A printing pad is then momentarily lowered and pressed onto the inked image plate to lift ink off of the etched ink filled cavity onto the printing pad. The ink so lifted defines the shape of the etched image. The inked pad is then momentarily lowered and pressed onto, for example, a golf ball, thereby releasing the ink from the pad to the golf ball. The ink released from the pad forms, on the spherical surface of the ball, an image corresponding to that of the etched cavity.
Printing pads are made from a resilient material, such as silicone rubber, which desirably picks up ink from the etched cavity of the image plate during lift-off and releases all of the ink lifted off when brought into contact with the article to be printed. Once the ink is deposited, it is cured, most commonly by a thermal curing process or by air drying (e.g., evaporation of solvent).
Many conventional golf ball printing processes include running UV curable inks in sealed cups without control of ink viscosity. The ink can thicken upon printing and become unusable and must be discarded. Solvent can be added manually, but thorough mixing is not possible without agitating the cup.
In addition, once inks are applied and if necessary, cured, all decorating methods are difficult to remove from the surface of the ball without further damaging the performance of the finished product. Golf balls that have defective logos from decaling or hot-stamping processes are further processed and made into “X-OUT” or practice balls. Nitrocellulose-based inks applied directly to ionomeric based golf ball covers can be removed via fine grit sandblasting, a method well known to the skilled artisan. All removal and further processing methods are not cost effective.
However, there remains a need for a method that monitors and adjusts ink viscosity during the printing process of golf balls. Such a method would reduce the amount of ink that becomes unusable.